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On Received Noise and RFI

13 Nov

As noted previously in this Blog I have been working on improving my received noise levels and eliminating any traces of RFI in my home due to transmitting RF from my Ham Station with any power level up to and including about 800 watts. I am clean of any RFI in my home save one TV fault that allows a Menu to pop up on the screen while I am sending CW on any of three bands. This I attribute to my antennas proximity to my house wiring and that I have not had an opportunity to go into my attic and place ferrite material on my AC wiring. This weekend may present an opportunity to get this done.

On receive I am measuring my noise floor by checking, almost daily, my received noise level on 20 Meters with my transceiver in AM mode with the receive bandwidth set at its maximum-in my case 9 KHz. If any readers recall last summer, while I changed some common mode choke configurations, I experienced a pop in my received noise levels form a norm of about S-5 to upwards of S-7. The XL graph is posted earlier in my Blog. Since that writing I have maintained a series of daily logbook records of my noise floor and am pleased to report that my noise floor is averaging S-5 to S-5.5 as before. This of course in AM mode at 9KHz bandwidth.

If all you listen to are S-9 signals then waste no time on noise abatement. If, however, you wish to wring out performance that others cannot do, then by all means go after noise abatement. During my daily schedules we suffer all the vagaries that Mom Nature can administer to an RF Circuit. It has been very helpful in maintaining my schedules as well as hearing things before others detect them. Kinda nice to be first. Do yourself a favor and open up your receiver. Listen to 20 M with your bandwidth as wide as possible; then take an S Meter reading. If your lucky you will see a reading of S-5 or below. If not then there is work to be done.

Thanks for reading and Best, Chas W7MAP/5

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Posted by on November 13, 2008 in Radio

 

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